CA2128013A1 - Method of hydrodehalogenating halogenated organic compounds in aqueous environmental sources - Google Patents
Method of hydrodehalogenating halogenated organic compounds in aqueous environmental sourcesInfo
- Publication number
- CA2128013A1 CA2128013A1 CA002128013A CA2128013A CA2128013A1 CA 2128013 A1 CA2128013 A1 CA 2128013A1 CA 002128013 A CA002128013 A CA 002128013A CA 2128013 A CA2128013 A CA 2128013A CA 2128013 A1 CA2128013 A1 CA 2128013A1
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- reaction
- hydrazine
- hydrogen gas
- organic compounds
- halogenated organic
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- A—HUMAN NECESSITIES
- A62—LIFE-SAVING; FIRE-FIGHTING
- A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
- A62D3/00—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances
- A62D3/30—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances by reacting with chemical agents
- A62D3/37—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances by reacting with chemical agents by reduction, e.g. hydrogenation
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/70—Treatment of water, waste water, or sewage by reduction
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
- C02F1/725—Treatment of water, waste water, or sewage by oxidation by catalytic oxidation
-
- A—HUMAN NECESSITIES
- A62—LIFE-SAVING; FIRE-FIGHTING
- A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
- A62D2101/00—Harmful chemical substances made harmless, or less harmful, by effecting chemical change
- A62D2101/04—Pesticides, e.g. insecticides, herbicides, fungicides or nematocides
-
- A—HUMAN NECESSITIES
- A62—LIFE-SAVING; FIRE-FIGHTING
- A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
- A62D2101/00—Harmful chemical substances made harmless, or less harmful, by effecting chemical change
- A62D2101/20—Organic substances
- A62D2101/22—Organic substances containing halogen
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Organic Chemistry (AREA)
- Health & Medical Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Toxicology (AREA)
- General Chemical & Material Sciences (AREA)
- Business, Economics & Management (AREA)
- Emergency Management (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Catalysts (AREA)
Abstract
A process for hydrodehalogenating halogenated organic compounds present in a contaminated aqueous environmental source in which the halogenated organic compounds are reacted with hydrogen gas or a source of hydrogen gas in the presence of a catalyst of palladium on carbon.
Description
W O 93/13831 2 ~ 2 ~ ~ ~ 3 PCT/US92/1~832 MET~OD OF ~YDRODEHALOGENATIMG ~ALOGENAT~D ORGANIC
CO~POUNDS JN AOUEOUS ENVIRO~ME~TAI. SOURCES
Field Of The Invention `
The present invention is generally directed to the hydrodehalogenation of halogenated organic compounds in an aqueous medium in which the compounds are reacted with hydrogen or a source of hydrogen in the presence of palladium on a carbon substrate preferably under mild temperature and pressure conditions. The present invention is particularly suited for the removal of chlorinated hydrocarbons from aqueous contaminated environmental sources such as waste water and hazardous waste sites.
Backaround Of The Invention The removal of halogenated organic ccmpounds from aqueous environmental sources including halogenated aromatic compounds such as chlorobenzenes and chlorophenols and halogenated aliphatic compounds such as methylene chloride, trichloroethanes and trichloroethylene has posed serious problems. Typically, the halogenated compounds have been disposed of by separating, such as by steam stripping, using a microporous hollow-fiber membrane, or carbon adsorption, the contaminants from their aqueous environment and then subjecting the resulting concentrated levels of contaminants to incineration. However, the combustion of halogenated organic compounds often results in the production of highly toxic by-products such as dioxins. Thus, incineration can itself become _5 an environmentally unsafe practice and its use for the àisposal W O 93/13831 2 1 ~ 8 3 1 3 PCT/US92/10832 of halogenated organic compounds problematical.
Industry has therefore looked to alternative techniques for the destruction of halogenated hydrocarbons found in the environment. Among the techniques which have been studied are ; biological treatment and chemical dehalogenation.
Chemical dehalogenation methods have been developed as an alternative to incineration and land disposal because they convert the halogenated organic co~pounds to less toxic non-halogenated compounds. One such process employs a sodium-naphthalene reagent to form sodium chloride and an inert sludge.While t~e sludge can be safely incinerated, the process is complicated by requirinq an air-free reaction vessel which limits its application for on-site treatment of contaminated environmental sources. In another approach, a dechlorination reagent is So Ded by reacting an alkali metal with polyethylene glycol in the presence of heat and oxygen.
T~e above-mentioned processes, which involve the oxidative dechlorination of halogenated organic compounds, are generally highly sensitive to water. Such processes require a separation step to remove the halogenated compounds from the aqueous environment before they can be treated. In addition, elevated temperatures are often required to carry out the reaction [See S. Tabaei et al., ~DehalogenatiOn of Organic Compounds" Tetra. Let. 32(24) pp. 2727-30 (Sept. 1991); M. Uhlir et al., "Recovery of Biphenyl by Catalytic Hydrogenolysis of Chlorinated Biphenyls" Chem. Abstr. 114 (23): 228496Z: and processes referred to in N. Surprenant et al., "Halogenated-Organic Containing Wastes" pp. 224-231 Noyes Data Corp. (1988)].
2l2~a~3 Accordingly, these processes have not been widely accepted for the decontamination of environmental sites.
There has been developed a reductive process for the dehalogenation of halogenated organic compounds. J.F.A. Kitchen, U.S. Patent No. 4,144,152 discloses a process for the treatment of halogenated organic compounds with W radiation and hydrogen in the absence of an oxidizing agent. While this process may be conducted in an aqueous environment, the requirement of a W
radiation reactor has made liqht activated reduction of chemicals (LARC) processes of the type disclosed in U.S. Patent No. -4,144,152 of li~ited commercial value.
~here is therefore a need for processes in which halogenated organic compounds can be removed directly from aqueous contaminated environmental sources in a safe and cost lS effective manner. Such processes should be able to be conducted under mild reaction conditions and be effective in treating contaminated sources having very low concentrations of contaminants as is likely to be found in waste streams.
Summarv Of The Invention The present invention is directed to a process of hydrodehalogenating haloqenated organic compounds and particularly those typically found in aqueous contaminated environmental sources such as waste streams and the ground water found at hazardous waste disposal sites. In accordance with the invention, the halogenated organic compounds are removed directly from the aqueous environment, without expensive radiation 2 ~ a 1 3 4 equipment, in a cost effective manner.
The concentration of the contaminants which may be treated in the present process can be in the parts per ~illion range. Specifically, the present invention can treat aqueous streams containing as little as 2 ppm of conta~inants. Of course, the process described herein is effective in treating waste streams containing much higher concentrations of halogenated contaminants on the order of l,000 ppm or more.
Typical aqueous waste streams have a halogenated organic content of about lO0 to 200 ppm.
In particular, the halogenated organic compounds, particularly chlorinated hydrocarbons, are reacted with hydrogen gas or a source of hydrogen gas in the presence of a catalyst consisting essentially of palladium on a carbon substrate. The reaction is conducted directly on the waste stream without a prior separation step to convert the halogenated hydrocarbons to less toxic hydrocarbons. A by-product of the reaction is hydrogen chloride which is produced in environmentally safe concentrations. The present invention therefore provides a safe and economically feasible method of treating sources of environmental pollution.
'~ L 2 ~
Detailed Description Of The Inv~tion ~.
The present invention is based on the surprising finding that halogenated organic compounds, particularly substituted and unsub~tituted chlorinated aliphatic and aromatic hydrocarbons can be hydrodehalogenated in situ in an aqueous medium by reduction with hydrogen in the presence of a catalyst of palladium on a carbon substrate. As used herein "palladium"
means elemental palladium or a palladium compound (e.g. palladium oxide) which can be reduced in the presence of hydrogen gas or a source of hydrogen gas. Because carbon is hydrophobic, it was surprising to find that carbon could be used effectively as a substrate for palladium in an aqueous medium to dechlorinate low concentrations of halogenated hydrocarbons.
The carbon substrates may be any of those customarily employed to support a noble metal catalyst. The amount of palladium metal on the carbon substrate is generally in the range of from 2 to 10% by weight, preferably a~out 5% by weight.
Higher concentrations of palladium may be used, but any reaction rate increase is substantially offset by the increased cost of the palladium. The amount of the catalyst employed in the reaction varies depending on the concentration of halogenated hydrocarbon.
Hydrogen is supplied to the reaction as a gas or in the form of a compound capable of delivering hydrogen gas. The preferred compounds for this purpose are hydrazine, hydrazine compounds and borohydrides. The hydrazine compounds include, for example, hydrazine hydrate, hydrazine sulfate, hydrazine chloride ~. 2~13 and the like. Alkali metal borohydrides such as sodium borohydride and potassium borohydride are the preferred borohydride sources of hydrogen. The amount of hydrogen used in the reaction should be sufficient to replace the removed chloride ions with hydrogen and is therefore at or above a stoichiometric amount.
In accordance with the invention, it is preferred to employ hydrogen gas as the reducing aqent when hydrodehalogenating aliphatic halogenated compounds such as methylene chloride and dichloroethane. Both hydrogen gas and other sources of hydrogen such as hydrazine can be used to hydrodehalogenate aromatic halogenated compounds such as chlorobenzene and chlorophenols.
A basic proton acceptor may optionally be employed to assist the reaction when the aqueous stream con~ains higher concentrations (e.g. at least lO0 ppm) of the halogenated organic compounds, and/or when aromatic compounds are present. Examples of the basic proton acceptor include ammonium hydroxide, sodium hydroxide, sodium acetate and organic amines such as triethylamine. Ammonium hydroxide is the preferred proton acceptor. The proton acceptor is preferably added in an amount equal to or exceeding a stoichiometric amount.
The reduction reaction of the present invention is preferably conducted under mild temperature and pressure conditions. The temperature of the reaction may be as low as ambient temperature. The upper tempe~ature is limited by the boiling point of the aqueous stream, the halogenated compounds contained therein, and/or the type of reactor. The upper W O 93/13831 2 1 ~ 3 PCT/US92/10832 temperature limit is also established by the decomposition temperature of hydrazine (120-C) and the other sources of hydrogen when tbey are used in the reaction. It is generally desirable to maintain the temperature of the reaction within the range of from ambient temperature to 50-C.
The reaction pressure is preferably maintained within the range of from atmospheric pressure to 50 psig. It is preferred to conduct the reaction at or near atmospheric pressure. On the other hand, if the reaction is conducted on waste streams containing more highly concentrated amounts of halogenated organic co~pounds, the reaction is preferably conducted at slightly elevated pressures of from lO to 50 psig.
The present invention may be employed to hydro-dehalogenate a wide variety of substituted and unsubstituted halogenated organic c~mpounds commonly found in contaminated environmental sources such as waste streams or the ground water found at hazard waste disposal sites. Among the compounds which are most commonly associated with these sources are cblorobenzenes, methylene chloride, trichloroethanes, trichloroethylene, chlorophenols and chlorinated pesticides including dichlorodiphenyltrichloroethane, Dieldrin, Aldrin, Toxaphene, Chlordane, Kepone and Mirex. The respective structures and chemical formulas of these pesticides are found in The ~ck Index, Ninth Edition (1976), incorporated herein by reference.
Chlorobenzenes are typically used as a chemical feed stock and solvent. Methylene chloride is currently employed as a paint remover, a degreasing solvent and as a chemical .
2:L2301~
processing solvent. Trichloroethanes are commonly used as a vapor degreaser for printed circuit boards and in metal cutting lubricants. Trichloroethylene is widely used as a deqreasing solvent and in t~e manufacture of polyvinylchloride.
Chlorophenols h~ve a number of com~ercial uses including antibacterial and germicidal agents, disinfectants and wood preservatives.
Accordingly, large amounts of these toxic chemicals are employed in industry and in agriculture. Their disposal has ~0 become of ~ajor interest to government and industry alike who are concerned with protecting the environment from contamination with hazardous waste. The present invention provides a safe and econo~ical means of detoxifying hazardous waste streams at the site of the conta~ination.
The types of reactors which may be used to carry out the process of the present invention are well known to those skilled in the art. Such reactors include fixed bed systems such as trickle-bed reactors, slurry bed reactors and the like. A
discussion of the operation of such reactors and their structural components are described in P.A. Ramachandran et al. "Three-Phase Catalytic Reactors~ (Gordon and Breach Science Publishers, 1983) and Charles Satterfeld, "Heterogenous Catalysis in Practice", Chap. XI, pp 312-369, McGraw Hill (1980), each incorporated herein by reference. -A trickle bed reactor generally includes a tube having a suitable catalyst such as a noble metal on a support packed along its entire length. The reactor has an inlet for receiving a liquid ~e.g. a waste stream) and bydrogen gas wbich are brought ~ 2~01~ ' W O 93/13831 PCT/US92tlO832 into contact and mixed optionally in the presence of an inert material such as ~-alumina. The liquid and hydrogen pass through the catalyst bed and the product (e.g. dehalogenated hydrocarbons) is taken fro~ the bottom of the reactor.
The following exa~ples are illustrative of embodiments of the invention and are not intended to limit the invention as encompassed by the claims forming part of the application.
ExamDle l .:~
A 550 ml sample of groundwater was taken from a test well at a remediation site where the aquifer had been contaminated with degreasing solvents. The water was filtered to remove suspended solids then analyzed and found to contain 132 pp~ trichloroethylene (TCE) and 7.5 ppm trichloroethane (TCA).
The contaminated groundwater was placed in a 1,000 ml Parr autocla~e using one gram/liter of prereduced 5% palladium on carbon (w/w) catalyst used in the form of a 50% water wet material (ESCAT 111 made by Engelhard Corporation). ~he dechlorination reaction was carried out at 23-C under a hydrogen pressure of 25 psig and at a stirring rate of 750 rpm. After two hours, the concentration of trichlorethylene decreased to 0.8 pp~
and the trichloroethane was no longer detectable. The chloride ion content of the water was analyzed and the results corresponded to a 93% conversion of the chlorinated compounds to the correspondinq non-chlorinated compounds.
W O 93/13831 PCT/US92~10832 2~ al3 ExamJ2le 2 An aqueous solution containin~ 660 mg/l of monochlorobenzene was placed in an autoclave with one g/l of She 5% palladium on carbon catalyst employed in Example 1. The temperature of the solution was raised slightly to 30-C and the autoclave was pressurized with hydrogen to 45 psig. After thirty minutes, the chloride level in the solution increased to an amount which corresponded to a 55% dehalogenation of chlorobenzene.
ExamDles 3-9 A contaminated waste stream containing 186.3 ppm of trichloroethane was fed into a trickle bed reactor at rates varying from 0.024 to 0.46 ml/sec.
The reactor contained a 2.54 cm diameter reactor tube packed with 31.4 gm of a non-prereduced 0.8~ w/w palladium on granular carbon catalyst (ESCAT 18 made by Engelhard Corporation) having an average particle size of 0.45 mm. The density of the catalyst bed was 0.503 gm/cm3 and the catalyst volume was 62.3 ml.
Hydrogen gas was supplied to the reactor at rates varying from 2.5 to 13 ml/sec. The rate of delivery of hydrogen was in excess and proportional to the flow rate of the waste stream. The reactor was maintained at a temperature of 24-C.
The chloride ion concentration as well as the 2s trichloroethane concentration were measured at the outlet of the reactor and the conversion of trichloroethane to non-chlorinated products was determined and the results are shown in table 1.
W 0 93/13831 1~ 2 1 2 8 0 1 3 PCT/US92/10832 _ .__ ..... - . I
EX~MPLE LIOUID FLOWCHLORIDE ION TC~ CONVERSION
RAl~CONCENlR~llON CONCENTRAllON
(mUs) IN OUI~T IN OUIl_EI' l (w~n) (ppm) I ~-3 0.024 ~20.36 35.4 81 I
_ I
CO~POUNDS JN AOUEOUS ENVIRO~ME~TAI. SOURCES
Field Of The Invention `
The present invention is generally directed to the hydrodehalogenation of halogenated organic compounds in an aqueous medium in which the compounds are reacted with hydrogen or a source of hydrogen in the presence of palladium on a carbon substrate preferably under mild temperature and pressure conditions. The present invention is particularly suited for the removal of chlorinated hydrocarbons from aqueous contaminated environmental sources such as waste water and hazardous waste sites.
Backaround Of The Invention The removal of halogenated organic ccmpounds from aqueous environmental sources including halogenated aromatic compounds such as chlorobenzenes and chlorophenols and halogenated aliphatic compounds such as methylene chloride, trichloroethanes and trichloroethylene has posed serious problems. Typically, the halogenated compounds have been disposed of by separating, such as by steam stripping, using a microporous hollow-fiber membrane, or carbon adsorption, the contaminants from their aqueous environment and then subjecting the resulting concentrated levels of contaminants to incineration. However, the combustion of halogenated organic compounds often results in the production of highly toxic by-products such as dioxins. Thus, incineration can itself become _5 an environmentally unsafe practice and its use for the àisposal W O 93/13831 2 1 ~ 8 3 1 3 PCT/US92/10832 of halogenated organic compounds problematical.
Industry has therefore looked to alternative techniques for the destruction of halogenated hydrocarbons found in the environment. Among the techniques which have been studied are ; biological treatment and chemical dehalogenation.
Chemical dehalogenation methods have been developed as an alternative to incineration and land disposal because they convert the halogenated organic co~pounds to less toxic non-halogenated compounds. One such process employs a sodium-naphthalene reagent to form sodium chloride and an inert sludge.While t~e sludge can be safely incinerated, the process is complicated by requirinq an air-free reaction vessel which limits its application for on-site treatment of contaminated environmental sources. In another approach, a dechlorination reagent is So Ded by reacting an alkali metal with polyethylene glycol in the presence of heat and oxygen.
T~e above-mentioned processes, which involve the oxidative dechlorination of halogenated organic compounds, are generally highly sensitive to water. Such processes require a separation step to remove the halogenated compounds from the aqueous environment before they can be treated. In addition, elevated temperatures are often required to carry out the reaction [See S. Tabaei et al., ~DehalogenatiOn of Organic Compounds" Tetra. Let. 32(24) pp. 2727-30 (Sept. 1991); M. Uhlir et al., "Recovery of Biphenyl by Catalytic Hydrogenolysis of Chlorinated Biphenyls" Chem. Abstr. 114 (23): 228496Z: and processes referred to in N. Surprenant et al., "Halogenated-Organic Containing Wastes" pp. 224-231 Noyes Data Corp. (1988)].
2l2~a~3 Accordingly, these processes have not been widely accepted for the decontamination of environmental sites.
There has been developed a reductive process for the dehalogenation of halogenated organic compounds. J.F.A. Kitchen, U.S. Patent No. 4,144,152 discloses a process for the treatment of halogenated organic compounds with W radiation and hydrogen in the absence of an oxidizing agent. While this process may be conducted in an aqueous environment, the requirement of a W
radiation reactor has made liqht activated reduction of chemicals (LARC) processes of the type disclosed in U.S. Patent No. -4,144,152 of li~ited commercial value.
~here is therefore a need for processes in which halogenated organic compounds can be removed directly from aqueous contaminated environmental sources in a safe and cost lS effective manner. Such processes should be able to be conducted under mild reaction conditions and be effective in treating contaminated sources having very low concentrations of contaminants as is likely to be found in waste streams.
Summarv Of The Invention The present invention is directed to a process of hydrodehalogenating haloqenated organic compounds and particularly those typically found in aqueous contaminated environmental sources such as waste streams and the ground water found at hazardous waste disposal sites. In accordance with the invention, the halogenated organic compounds are removed directly from the aqueous environment, without expensive radiation 2 ~ a 1 3 4 equipment, in a cost effective manner.
The concentration of the contaminants which may be treated in the present process can be in the parts per ~illion range. Specifically, the present invention can treat aqueous streams containing as little as 2 ppm of conta~inants. Of course, the process described herein is effective in treating waste streams containing much higher concentrations of halogenated contaminants on the order of l,000 ppm or more.
Typical aqueous waste streams have a halogenated organic content of about lO0 to 200 ppm.
In particular, the halogenated organic compounds, particularly chlorinated hydrocarbons, are reacted with hydrogen gas or a source of hydrogen gas in the presence of a catalyst consisting essentially of palladium on a carbon substrate. The reaction is conducted directly on the waste stream without a prior separation step to convert the halogenated hydrocarbons to less toxic hydrocarbons. A by-product of the reaction is hydrogen chloride which is produced in environmentally safe concentrations. The present invention therefore provides a safe and economically feasible method of treating sources of environmental pollution.
'~ L 2 ~
Detailed Description Of The Inv~tion ~.
The present invention is based on the surprising finding that halogenated organic compounds, particularly substituted and unsub~tituted chlorinated aliphatic and aromatic hydrocarbons can be hydrodehalogenated in situ in an aqueous medium by reduction with hydrogen in the presence of a catalyst of palladium on a carbon substrate. As used herein "palladium"
means elemental palladium or a palladium compound (e.g. palladium oxide) which can be reduced in the presence of hydrogen gas or a source of hydrogen gas. Because carbon is hydrophobic, it was surprising to find that carbon could be used effectively as a substrate for palladium in an aqueous medium to dechlorinate low concentrations of halogenated hydrocarbons.
The carbon substrates may be any of those customarily employed to support a noble metal catalyst. The amount of palladium metal on the carbon substrate is generally in the range of from 2 to 10% by weight, preferably a~out 5% by weight.
Higher concentrations of palladium may be used, but any reaction rate increase is substantially offset by the increased cost of the palladium. The amount of the catalyst employed in the reaction varies depending on the concentration of halogenated hydrocarbon.
Hydrogen is supplied to the reaction as a gas or in the form of a compound capable of delivering hydrogen gas. The preferred compounds for this purpose are hydrazine, hydrazine compounds and borohydrides. The hydrazine compounds include, for example, hydrazine hydrate, hydrazine sulfate, hydrazine chloride ~. 2~13 and the like. Alkali metal borohydrides such as sodium borohydride and potassium borohydride are the preferred borohydride sources of hydrogen. The amount of hydrogen used in the reaction should be sufficient to replace the removed chloride ions with hydrogen and is therefore at or above a stoichiometric amount.
In accordance with the invention, it is preferred to employ hydrogen gas as the reducing aqent when hydrodehalogenating aliphatic halogenated compounds such as methylene chloride and dichloroethane. Both hydrogen gas and other sources of hydrogen such as hydrazine can be used to hydrodehalogenate aromatic halogenated compounds such as chlorobenzene and chlorophenols.
A basic proton acceptor may optionally be employed to assist the reaction when the aqueous stream con~ains higher concentrations (e.g. at least lO0 ppm) of the halogenated organic compounds, and/or when aromatic compounds are present. Examples of the basic proton acceptor include ammonium hydroxide, sodium hydroxide, sodium acetate and organic amines such as triethylamine. Ammonium hydroxide is the preferred proton acceptor. The proton acceptor is preferably added in an amount equal to or exceeding a stoichiometric amount.
The reduction reaction of the present invention is preferably conducted under mild temperature and pressure conditions. The temperature of the reaction may be as low as ambient temperature. The upper tempe~ature is limited by the boiling point of the aqueous stream, the halogenated compounds contained therein, and/or the type of reactor. The upper W O 93/13831 2 1 ~ 3 PCT/US92/10832 temperature limit is also established by the decomposition temperature of hydrazine (120-C) and the other sources of hydrogen when tbey are used in the reaction. It is generally desirable to maintain the temperature of the reaction within the range of from ambient temperature to 50-C.
The reaction pressure is preferably maintained within the range of from atmospheric pressure to 50 psig. It is preferred to conduct the reaction at or near atmospheric pressure. On the other hand, if the reaction is conducted on waste streams containing more highly concentrated amounts of halogenated organic co~pounds, the reaction is preferably conducted at slightly elevated pressures of from lO to 50 psig.
The present invention may be employed to hydro-dehalogenate a wide variety of substituted and unsubstituted halogenated organic c~mpounds commonly found in contaminated environmental sources such as waste streams or the ground water found at hazard waste disposal sites. Among the compounds which are most commonly associated with these sources are cblorobenzenes, methylene chloride, trichloroethanes, trichloroethylene, chlorophenols and chlorinated pesticides including dichlorodiphenyltrichloroethane, Dieldrin, Aldrin, Toxaphene, Chlordane, Kepone and Mirex. The respective structures and chemical formulas of these pesticides are found in The ~ck Index, Ninth Edition (1976), incorporated herein by reference.
Chlorobenzenes are typically used as a chemical feed stock and solvent. Methylene chloride is currently employed as a paint remover, a degreasing solvent and as a chemical .
2:L2301~
processing solvent. Trichloroethanes are commonly used as a vapor degreaser for printed circuit boards and in metal cutting lubricants. Trichloroethylene is widely used as a deqreasing solvent and in t~e manufacture of polyvinylchloride.
Chlorophenols h~ve a number of com~ercial uses including antibacterial and germicidal agents, disinfectants and wood preservatives.
Accordingly, large amounts of these toxic chemicals are employed in industry and in agriculture. Their disposal has ~0 become of ~ajor interest to government and industry alike who are concerned with protecting the environment from contamination with hazardous waste. The present invention provides a safe and econo~ical means of detoxifying hazardous waste streams at the site of the conta~ination.
The types of reactors which may be used to carry out the process of the present invention are well known to those skilled in the art. Such reactors include fixed bed systems such as trickle-bed reactors, slurry bed reactors and the like. A
discussion of the operation of such reactors and their structural components are described in P.A. Ramachandran et al. "Three-Phase Catalytic Reactors~ (Gordon and Breach Science Publishers, 1983) and Charles Satterfeld, "Heterogenous Catalysis in Practice", Chap. XI, pp 312-369, McGraw Hill (1980), each incorporated herein by reference. -A trickle bed reactor generally includes a tube having a suitable catalyst such as a noble metal on a support packed along its entire length. The reactor has an inlet for receiving a liquid ~e.g. a waste stream) and bydrogen gas wbich are brought ~ 2~01~ ' W O 93/13831 PCT/US92tlO832 into contact and mixed optionally in the presence of an inert material such as ~-alumina. The liquid and hydrogen pass through the catalyst bed and the product (e.g. dehalogenated hydrocarbons) is taken fro~ the bottom of the reactor.
The following exa~ples are illustrative of embodiments of the invention and are not intended to limit the invention as encompassed by the claims forming part of the application.
ExamDle l .:~
A 550 ml sample of groundwater was taken from a test well at a remediation site where the aquifer had been contaminated with degreasing solvents. The water was filtered to remove suspended solids then analyzed and found to contain 132 pp~ trichloroethylene (TCE) and 7.5 ppm trichloroethane (TCA).
The contaminated groundwater was placed in a 1,000 ml Parr autocla~e using one gram/liter of prereduced 5% palladium on carbon (w/w) catalyst used in the form of a 50% water wet material (ESCAT 111 made by Engelhard Corporation). ~he dechlorination reaction was carried out at 23-C under a hydrogen pressure of 25 psig and at a stirring rate of 750 rpm. After two hours, the concentration of trichlorethylene decreased to 0.8 pp~
and the trichloroethane was no longer detectable. The chloride ion content of the water was analyzed and the results corresponded to a 93% conversion of the chlorinated compounds to the correspondinq non-chlorinated compounds.
W O 93/13831 PCT/US92~10832 2~ al3 ExamJ2le 2 An aqueous solution containin~ 660 mg/l of monochlorobenzene was placed in an autoclave with one g/l of She 5% palladium on carbon catalyst employed in Example 1. The temperature of the solution was raised slightly to 30-C and the autoclave was pressurized with hydrogen to 45 psig. After thirty minutes, the chloride level in the solution increased to an amount which corresponded to a 55% dehalogenation of chlorobenzene.
ExamDles 3-9 A contaminated waste stream containing 186.3 ppm of trichloroethane was fed into a trickle bed reactor at rates varying from 0.024 to 0.46 ml/sec.
The reactor contained a 2.54 cm diameter reactor tube packed with 31.4 gm of a non-prereduced 0.8~ w/w palladium on granular carbon catalyst (ESCAT 18 made by Engelhard Corporation) having an average particle size of 0.45 mm. The density of the catalyst bed was 0.503 gm/cm3 and the catalyst volume was 62.3 ml.
Hydrogen gas was supplied to the reactor at rates varying from 2.5 to 13 ml/sec. The rate of delivery of hydrogen was in excess and proportional to the flow rate of the waste stream. The reactor was maintained at a temperature of 24-C.
The chloride ion concentration as well as the 2s trichloroethane concentration were measured at the outlet of the reactor and the conversion of trichloroethane to non-chlorinated products was determined and the results are shown in table 1.
W 0 93/13831 1~ 2 1 2 8 0 1 3 PCT/US92/10832 _ .__ ..... - . I
EX~MPLE LIOUID FLOWCHLORIDE ION TC~ CONVERSION
RAl~CONCENlR~llON CONCENTRAllON
(mUs) IN OUI~T IN OUIl_EI' l (w~n) (ppm) I ~-3 0.024 ~20.36 35.4 81 I
_ I
4 0.041 95.07 67.13 ~3.g7 _ _ _ . . _ _ _ 0.063 71.00 97.~0 _47.78 I . __ _ _ -.
6 0.088 53.46 119.28 35.97 I _. _ _ 7 0.1475 35.64 141.82 23.98 _ 8 0.2936 20.29 160.87 14.07 9 0.46 10.40 173.26 7.0 , _ _ _ As shown in Table 1, the process of the present invention is very effective in converting trichloroethane to non-chlorinated compounds particularly at the slower feed rates of those tested. For example, the concentration of trichloroethane in the waste stream was reduced from 186.3 pp~ to 35.4 ppm (81~
conversion) with a single pass through the reactor. Improved conversions can be obtained by recycling the treated waste stream through the reactor, increasing the residence time, increasing the reaction temperature or combination thereof.
As further shown in TABTF 1, the amount of chlorinated hydrocarbon removal is substantially inversely proportional to the feed rate. Accordingly, a particular feed rate may be selected which will obtain the desired reduction in trichloroethane content by a single or multiple pass.
~3D ~ ~3 The procedure carried out in Examples 3-9 was repeated using a waste stream having a trichloroethane concentration of 103 ppm. The results are shown in Table 2.
~ v ~
EX~MPLE LIOUID FLOW CHLORlDE lOtl TCA CONVERSION
R~l~CONCEN~nONCONOENlRAnON %
(~h)IN ounErIN oun~r I . , (W~) ~ppm) 0.02461.73 25.75 75.00 :
11 0.04152.98 36.59 64.48 _ _ 12 0.14751~.07 79.10 23.21 13 0.21714 24 85.15 17.33 _ 14 0.293610.93 89.27 13.33 0.3759.62 90.94 11.71 16 0.46 5.47 96.13 6.67 .. .
The results in Tables 1 and 2 show that the extent of the hydrodehalogenation reaction is independent of inlet concentration. The chlorinated hydrocarbon level in the resulting fluid can be reduced further or even eliminated by increasing the residence time, the number of passes through the catalyst bed, the reaction temperature or combination thereof.
W O 93/13831 t3 PCT/U592/10832 The procedure carried out in Examples 3 9 was substantially repeated on a waste stream having a concentration of trichloroethylene of 105.3 ppm. T~e results are shown in Table 3.
~ABLE 3 _ .
EX~Mpl F LK~UID FLOWCHLORIDE ION TCE CONVERS10N
R~TE CONCENlRAnON CONCEN'I~ON %
(~Ih) IN OUI'LFI' IN OUll~
(ppm) (pplD) I ~:
17 0.038 75.98 11.50 89.08 18 _ 0.04~_ 72.63 lS.63 85.15 19 0.088 54.90 37.52 64.37 _ I
_ 0.1475 37.62 58.86 44.11 21 _ 0.2936 22.45 77.58 26.32 22 0.435 19.73 80.91 23.16 . . ................. _, _ The procedure of Examples 3-9 were substantially repeated on a waste Stream having a concentration of tric~loroethylene of 152.8 ppm. The results are shown in Table 4.
a l 3 ~ .
EXAM~LELI~UID FLOW CHLORIDE ION TCE CONVERSION
R~l~CONCENlR~nON CONa~lR~nON 9 (mU~) IN OUll~T IN OUll EI' (PP~) (W~) 24 0 038 118.55 7,33 _ 95.2 ~ 0.063 101.02 28.08 81.62 I
26 0.088 84.62 48.33 68.37 27 0 1475 57.18 ~82.21 46.20 I ~
28 0.2g36 33.66 111.24 27.20 I ~-,-29 0.435 27.37 119.02 22.11 E~AMPLE 30 A 1,000 ml Parr autoclave was charged in air with 5.00g (38.9 mmol) of 4-chlorophenol, 2.9 ml (42.9 mmol) of ammonium hydroxide, 0.450 of 5% palladium on carbon (ESCAT 111 manufactured by Engelhard Corporation), and 500 ml of water. The autoclave was then sealed and connected to a gas delivery system containing a gas manifold, a gas regulator for maintaining constant hydrogen pressure within the autoclave, and a calibrated, 500 ml gas reservoir for monitoring hydrogen consumption during the course of the reaotion. The reservoir pressure was maintained at 70 psi while the autoclave pressure was maintained at 35 psi. The gas delivery system (manifold and reservoir) was charged and vented three times with argon and then charged a fourth time with argon. The autoclave then was purged with argon in a similar manner and heated under pressure to 35 C
via an external, constant temperature heating bath.
WO 93/13831 2 1 2 8 ~ 1 3 PCT/US92/10832 Subsequently, the gas delivery system and autoclave were purged with hydrogen three times by the same charge/vent procedure described previously. After charging the autoclave a fourth time with hydrogen, mechanical stirring was started (520 rpm), and the reservoir was isolated from the tank gas supply via a shut-off valve in the maniol~ system. The pressure drop in the gas reservoir was monitored via a strip chart recorder and digital pressure readout. The reaction mixture was sa~pled periodically and its composition was assayed by gas chromatography. The initial rate over the first 1.2 minutes of reaction was obtained from the hydrogen consumption curve, and a quantitative phenol yield was determined by gas chromatography.
The results are shown in Table 5.
15A 1,000 ml Parr autocla~e was charged in air with 5.00g (38.9 mmol) of 4-chlorophenol, 4.2 ml (62.1 mmol) of ammonium hydroxide, 0.225g of ESCAT 111, 2.70g (85% w/w, 45.8 mmol) of hydrazine hydrate, and 500 ml of water. The autoclave was sealed without pressurizing or purging, and mechanical stirring ~520 rpm) was begun immediately. The reaction mixture was sampled periodically and its composition was assayed by gas chromatography. Quantitative phenol yield as a function of time was determined by gas chromatography and the data was fit to a ~ simple first order kinetic expression. The results are shown in Table 5.
WO 93/13831 PCI`/USg2/10832 O :1 3 b~ ' _ _ :
:~ ~
~ U~ U~ ;' _ _ O N
6 0.088 53.46 119.28 35.97 I _. _ _ 7 0.1475 35.64 141.82 23.98 _ 8 0.2936 20.29 160.87 14.07 9 0.46 10.40 173.26 7.0 , _ _ _ As shown in Table 1, the process of the present invention is very effective in converting trichloroethane to non-chlorinated compounds particularly at the slower feed rates of those tested. For example, the concentration of trichloroethane in the waste stream was reduced from 186.3 pp~ to 35.4 ppm (81~
conversion) with a single pass through the reactor. Improved conversions can be obtained by recycling the treated waste stream through the reactor, increasing the residence time, increasing the reaction temperature or combination thereof.
As further shown in TABTF 1, the amount of chlorinated hydrocarbon removal is substantially inversely proportional to the feed rate. Accordingly, a particular feed rate may be selected which will obtain the desired reduction in trichloroethane content by a single or multiple pass.
~3D ~ ~3 The procedure carried out in Examples 3-9 was repeated using a waste stream having a trichloroethane concentration of 103 ppm. The results are shown in Table 2.
~ v ~
EX~MPLE LIOUID FLOW CHLORlDE lOtl TCA CONVERSION
R~l~CONCEN~nONCONOENlRAnON %
(~h)IN ounErIN oun~r I . , (W~) ~ppm) 0.02461.73 25.75 75.00 :
11 0.04152.98 36.59 64.48 _ _ 12 0.14751~.07 79.10 23.21 13 0.21714 24 85.15 17.33 _ 14 0.293610.93 89.27 13.33 0.3759.62 90.94 11.71 16 0.46 5.47 96.13 6.67 .. .
The results in Tables 1 and 2 show that the extent of the hydrodehalogenation reaction is independent of inlet concentration. The chlorinated hydrocarbon level in the resulting fluid can be reduced further or even eliminated by increasing the residence time, the number of passes through the catalyst bed, the reaction temperature or combination thereof.
W O 93/13831 t3 PCT/U592/10832 The procedure carried out in Examples 3 9 was substantially repeated on a waste stream having a concentration of trichloroethylene of 105.3 ppm. T~e results are shown in Table 3.
~ABLE 3 _ .
EX~Mpl F LK~UID FLOWCHLORIDE ION TCE CONVERS10N
R~TE CONCENlRAnON CONCEN'I~ON %
(~Ih) IN OUI'LFI' IN OUll~
(ppm) (pplD) I ~:
17 0.038 75.98 11.50 89.08 18 _ 0.04~_ 72.63 lS.63 85.15 19 0.088 54.90 37.52 64.37 _ I
_ 0.1475 37.62 58.86 44.11 21 _ 0.2936 22.45 77.58 26.32 22 0.435 19.73 80.91 23.16 . . ................. _, _ The procedure of Examples 3-9 were substantially repeated on a waste Stream having a concentration of tric~loroethylene of 152.8 ppm. The results are shown in Table 4.
a l 3 ~ .
EXAM~LELI~UID FLOW CHLORIDE ION TCE CONVERSION
R~l~CONCENlR~nON CONa~lR~nON 9 (mU~) IN OUll~T IN OUll EI' (PP~) (W~) 24 0 038 118.55 7,33 _ 95.2 ~ 0.063 101.02 28.08 81.62 I
26 0.088 84.62 48.33 68.37 27 0 1475 57.18 ~82.21 46.20 I ~
28 0.2g36 33.66 111.24 27.20 I ~-,-29 0.435 27.37 119.02 22.11 E~AMPLE 30 A 1,000 ml Parr autoclave was charged in air with 5.00g (38.9 mmol) of 4-chlorophenol, 2.9 ml (42.9 mmol) of ammonium hydroxide, 0.450 of 5% palladium on carbon (ESCAT 111 manufactured by Engelhard Corporation), and 500 ml of water. The autoclave was then sealed and connected to a gas delivery system containing a gas manifold, a gas regulator for maintaining constant hydrogen pressure within the autoclave, and a calibrated, 500 ml gas reservoir for monitoring hydrogen consumption during the course of the reaotion. The reservoir pressure was maintained at 70 psi while the autoclave pressure was maintained at 35 psi. The gas delivery system (manifold and reservoir) was charged and vented three times with argon and then charged a fourth time with argon. The autoclave then was purged with argon in a similar manner and heated under pressure to 35 C
via an external, constant temperature heating bath.
WO 93/13831 2 1 2 8 ~ 1 3 PCT/US92/10832 Subsequently, the gas delivery system and autoclave were purged with hydrogen three times by the same charge/vent procedure described previously. After charging the autoclave a fourth time with hydrogen, mechanical stirring was started (520 rpm), and the reservoir was isolated from the tank gas supply via a shut-off valve in the maniol~ system. The pressure drop in the gas reservoir was monitored via a strip chart recorder and digital pressure readout. The reaction mixture was sa~pled periodically and its composition was assayed by gas chromatography. The initial rate over the first 1.2 minutes of reaction was obtained from the hydrogen consumption curve, and a quantitative phenol yield was determined by gas chromatography.
The results are shown in Table 5.
15A 1,000 ml Parr autocla~e was charged in air with 5.00g (38.9 mmol) of 4-chlorophenol, 4.2 ml (62.1 mmol) of ammonium hydroxide, 0.225g of ESCAT 111, 2.70g (85% w/w, 45.8 mmol) of hydrazine hydrate, and 500 ml of water. The autoclave was sealed without pressurizing or purging, and mechanical stirring ~520 rpm) was begun immediately. The reaction mixture was sampled periodically and its composition was assayed by gas chromatography. Quantitative phenol yield as a function of time was determined by gas chromatography and the data was fit to a ~ simple first order kinetic expression. The results are shown in Table 5.
WO 93/13831 PCI`/USg2/10832 O :1 3 b~ ' _ _ :
:~ ~
~ U~ U~ ;' _ _ O N
Claims (9)
1. A method of hydrodehalogenating chlorinated aliphatic hydrocarbons from a substantially aqueous contaminated waste stream suspected of containing halogenated hydrocarbons comprising passing the waste stream into contact with hydrogen gas or a source of hydrogen gas selected from hydrazine, hydrazine hydrate, hydrazine salts and borohydrides in the presence of a catalyst consisting essentially of palladium on carbon at a temperature of from ambient temperature to 50°C and at a pressure of from atmospheric pressure to 50 psig.
2. The method of claim 1 wherein the reaction is conducted at a pressure of from atmospheric pressure to 50 psig.
3. The method of claim 1 wherein the reaction is conducted at a temperature of from ambient temperature to 50°C.
4. The method of claim 1 further comprising conducting the reaction in the presence of a basic proton acceptor chosen from among ammonium hydroxide, sodium hydroxide, sodium acetate and organic amines.
5. The method of claim 4 wherein the basic proton acceptor is ammonium hydroxide.
6. The method of claim 5 wherein the amount of the basic proton acceptor is equal to or in excess of a stoichiometric amount.
7. The method of claim 1 comprising treating and medium with an amount of hydrogen gas equal to or in excess of a stoichiometric amount.
8. The method of claim 1 wherein the source of hydrogen gas is selected from the group consisting of hydrazine, hydrazine hydrate, hydrazine salts and borohydrides.
9. The method of claim 1 wherein the waste stream includes at least one halogenated compound selected from the group consisting of trichloroethanes, trichloroethylene, methylene chloride.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/820,458 US5196617A (en) | 1992-01-14 | 1992-01-14 | Method of hydrodehalogenating halogenated organic compounds in aqueous environmental sources |
| US820,458 | 1992-01-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2128013A1 true CA2128013A1 (en) | 1993-07-22 |
Family
ID=25230811
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002128013A Abandoned CA2128013A1 (en) | 1992-01-14 | 1992-12-11 | Method of hydrodehalogenating halogenated organic compounds in aqueous environmental sources |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US5196617A (en) |
| EP (1) | EP0623034A1 (en) |
| JP (1) | JPH07503176A (en) |
| CA (1) | CA2128013A1 (en) |
| WO (1) | WO1993013831A1 (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1994014731A1 (en) * | 1992-12-23 | 1994-07-07 | Commonwealth Scientific And Industrial Research Organisation | Destruction of halide containing organics and solvent purification |
| US5951852A (en) * | 1993-12-23 | 1999-09-14 | Commonwealth Scientific And Industrial Research Organisation Et Al. | Destruction of halide containing organics and solvent purification |
| US5600031A (en) * | 1995-08-18 | 1997-02-04 | Exxon Chemical Patents, Inc. | Process for preforming cobaltous salts using shell-type preformer catalysts |
| EP0933333B1 (en) * | 1998-02-02 | 2004-09-01 | I.M.E.S. Gesellschaft für Innovative Mess-, Erkundungs- und Sanierungstechnologien mbH | Use of a supported catalyst |
| FR2801808B1 (en) * | 1999-12-07 | 2002-05-17 | Atofina | PROCESS FOR REDUCING ELEMENTARY HALOGEN IN AN EFFLUENT AND INSTALLATION FOR IMPLEMENTING IT |
| ES2289942B1 (en) * | 2006-07-20 | 2008-12-16 | Universidad Autonoma De Madrid | CATALYTIC PROCESS FOR THE TREATMENT OF PAPER PASTE WHITENING EFFLUENTS. |
| EP2440515B1 (en) * | 2009-06-13 | 2018-08-15 | Archer-Daniels-Midland Company | Production of adipic acid and derivatives from carbohydrate-containing materials |
| US8669397B2 (en) | 2009-06-13 | 2014-03-11 | Rennovia, Inc. | Production of adipic acid and derivatives from carbohydrate-containing materials |
| CA2763177C (en) | 2009-06-13 | 2017-08-01 | Thomas R. Boussie | Production of glutaric acid and derivatives from carbohydrate-containing materials |
| US8669393B2 (en) * | 2010-03-05 | 2014-03-11 | Rennovia, Inc. | Adipic acid compositions |
| US9770705B2 (en) | 2010-06-11 | 2017-09-26 | Rennovia Inc. | Oxidation catalysts |
| US10752526B2 (en) * | 2012-02-12 | 2020-08-25 | Bluflow Technologies, Inc. | Method for destruction of reducible contaminants in waste or ground water |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2725405A (en) * | 1951-12-24 | 1955-11-29 | Dow Chemical Co | Selective reduction of chlorobromohydrocarbons |
| US2822617A (en) * | 1955-02-14 | 1958-02-11 | Frederick W Sampsel | Level |
| US2949491A (en) * | 1957-11-29 | 1960-08-16 | Hooker Chemical Corp | Selective hydrogenation of chlorobenzenes |
| US4351978A (en) * | 1980-07-21 | 1982-09-28 | Osaka Prefectural Government | Method for the disposal of polychlorinated biphenyls |
| FR2496639A1 (en) * | 1980-12-24 | 1982-06-25 | Rhone Poulenc Ind | PROCESS FOR THE PREPARATION OF METACHLORIC PHENOLS |
| US4618686A (en) * | 1984-09-27 | 1986-10-21 | Ciba-Geigy Corporation | Process for dehalogenation of aryl and alpha-araliphatic halides |
| US4909947A (en) * | 1986-03-03 | 1990-03-20 | Uop | Process for detoxifying high aqueous content hazardous waste streams |
| US4661179A (en) * | 1986-07-24 | 1987-04-28 | The United States Of America As Represented By The Secretary Of The Army | Destruction of waste explosive by hydrogenolysis |
| IL94397A (en) * | 1990-05-15 | 1994-10-07 | Israel Atomic Energy Comm | Process for the dehalogenation of organic compounds |
-
1992
- 1992-01-14 US US07/820,458 patent/US5196617A/en not_active Expired - Fee Related
- 1992-12-11 JP JP5512447A patent/JPH07503176A/en active Pending
- 1992-12-11 EP EP93901348A patent/EP0623034A1/en not_active Ceased
- 1992-12-11 WO PCT/US1992/010832 patent/WO1993013831A1/en not_active Application Discontinuation
- 1992-12-11 CA CA002128013A patent/CA2128013A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| WO1993013831A1 (en) | 1993-07-22 |
| JPH07503176A (en) | 1995-04-06 |
| EP0623034A1 (en) | 1994-11-09 |
| US5196617A (en) | 1993-03-23 |
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| Date | Code | Title | Description |
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